Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of cough and sinus congestion, often presenting with additional symptoms such as sneezing, runny nose, and mild fatigue. The short duration of 3 days supports this diagnosis, as viral URTIs typically resolve on their own within a week.

Allergic Rhinitis: Symptoms can include cough, sinus congestion, sneezing, and runny nose, especially if exposure to allergens has occurred. The history of symptoms and potential allergen exposure would guide this diagnosis.
Acute Sinusitis: Often follows a viral URTI, presenting with facial pain, nasal congestion, and purulent nasal discharge. The duration and severity of symptoms can help differentiate this from a simple URTI.
Acute Bronchitis: Characterized by a cough, often productive, following a viral infection. It can present with or without sinus congestion, depending on the involvement of the upper respiratory tract.

Pneumonia: Although less likely with a short duration of symptoms, pneumonia can present with cough and may have associated sinus congestion if there is an upper respiratory component. Fever, shortness of breath, and chest pain would be red flags.
Influenza: Especially during flu season, influenza can cause severe respiratory symptoms, including cough and sinus congestion, and is more likely to cause systemic symptoms like fever and significant fatigue.
Pertussis (Whooping Cough): Characterized by a distinctive whoop sound during coughing fits, pertussis is a critical diagnosis to consider, especially in unvaccinated or under-vaccinated individuals, due to its contagiousness and potential severity.

Tuberculosis (TB): A chronic infection that can cause cough, among other symptoms. It's less likely to present with acute sinus congestion but should be considered in individuals with risk factors (e.g., immunocompromised, recent travel to or from areas with high TB prevalence).
Fungal Sinusitis: More common in immunocompromised patients, presenting with chronic or severe sinus symptoms, including facial pain and nasal congestion. A rare but important consideration in the right clinical context.
Sarcoidosis: A systemic disease that can affect the lungs and sinuses, causing cough and sinus congestion among other symptoms. It's a diagnosis of exclusion and would require further investigation, including imaging and potentially biopsy.